Hadrian’s Wall- Was it a military failure?

In about 5 weeks’ time I will be 4 back again standing at the wall, this time with fresh eyes, having digested a lot more information about the early would be conquerers,the Romans, would be coz they never made Scotland Caledonia) part of their Empire.

The then tribes of Northern Scotland must have been a tough lot I reckon, and I believe the wall was built to keep them in not to keep them out, if you know what I mean. Aside that of course ...